1. Field of the Invention
The present invention relates to a technique of marking a golf ball.
2. Description of the Related Art
In general, a surface of a golf ball is marked with letters, numerical characters, graphics and the like in order to make the same be distinguishable from others. Marking is applied by printing with ink for a golf ball mainly composed of a urethane resin, for example, by means of pad printing, stamping of a solid transfer printing film, or thermal transfer using a transfer printing film. Since a golf ball is used under severe conditions, for example, it is hit by a club, abraded by sands in a bunker and collides against a barrier or a tree on the rough, an ink layer which forms marking is required to be excellent in hitting resistance (hardness to break or chip) and abrasion resistance (hardness to be scratched or hurt) in addition to adhesiveness to a ball (hardness to peel off).
Under these circumstances, it is a well known technique to use an ink resin for a golf ball which has a predetermined hydroxyl value as disclosed in Japanese Patent Laying-Open No. 7-89214 (Literature 1) and Japanese Patent Laying-Open No. 11-139095 (Literature 2). With this arrangement, in a case where after marking, the entire ball surface is coated with urethane, a hydroxyl group (—OH) in a marking ink layer and an isocyanate group (—NCO) in a urethane top coat layer react with each other to generate new urethane bonding between these layers to enhance protection of the ink layer.
With such ink as illustrated in Literature 2, however, because a softening temperature of the ink itself is lowered to enable transfer printing at a low temperature, abrasion resistance of the ink as of after the transfer printing is degraded, so that when a pattern printed on a golf ball surface is abraded after the transfer printing, the pattern is liable to be worn away.